Rotary drill bits in the oil patch industry currently have such short life that they are considered a disposable item. The bits must be raised from the drill hole for replacement at great expense and down-time. The mode of failure is too often caused by bearing failure rather than worn carbide tips. The seals currently used allow the lubricant pressure to build up to as high as 1500 psi. If the seal holds, this excess pressure accelerates bearing wear and/or can rupture the diaphragm. If the seal blows open, lubricant is lost immediately and drilling mud enters the bushing and bearing. Many types of seals have been tried to solve this problem from O-rings by polytetrafluoroethylene U-cups. No seal designs have had any real advantage over the common ordinary O-ring, which has the advantages of being less expensive and easy to install.
It is an object of the present invention to provide a shaft seal and method that will solve the problems discussed above.
It is another object of the present invention to provide a shaft seal that will relieve the excess pressure without starving the bushing and bearing of lubricant, while maintaining adequate pressure for proper lubrication and while still excluding drilling mud.
It is a further object of the present invention to extend bearing life and the life of the rotary drill bits.